1. Field of the Invention
The present invention relates to a system which controls various mechanisms, for an internal combustion engine, mounted on an automotive vehicle, and more particularly to apparatus for testing such a system.
2. Description of the Prior Art
Most conventional electronic control devices which control mechanisms, for an internal combustion engine, mounted on an automotive vehicle have been single function devices, such as, for example, an electronically controlled fuel injection device. In this prior art fuel injection device having only a single function, a means for testing the control device has been of a type which supplies predetermined dummy signals to the control device in order to obtain therefrom a control signal, e.g. the pulse duration for fuel injection, which is the determined and displayed.
Recently, a single control system has been put to practical use which includes a microcomputer and which effects a plurality of controls of fuel injection, spark advance angle, exhaust gas recirculation rate, etc. Such a control system includes relatively many sensors, actuators and considerably complicated wiring harnesses. Thus when a malfunction occurs in this control system, it takes considerable time and skill to find the malfunction. Further it is not easy to ascertain whether the system is operating completely. When a single control system is used in order to control several items in time sharing-mode, there are relatively many check items in a control unit itself to be used therein. Thus a testing apparatus is required which can test not only the control unit itself reliably and effectively but also the whole system except for the control unit.